Printer Circuit Boards (PCBs) include Copper conductors. Copper conductors may get oxidized. While copper oxidation does not cause PCB failures, the color change associated with the oxidation often causes many false alarms (false positives) during optical inspection.
Cupric Oxide, Cuprous Oxide, Copper Chloride and Copper Carbonate tend to absorb light and to be imaged as dark pixels that once compares to Copper cause false positives. Similar effects may occur in other oxidized metals in inspected objects.
Other chemical reactions may also result in color change, while not severely reducing the performance of the chemically reacted object (e.g. the copper conductors).
There is a growing need to provide robust optical inspection systems and methods that are less sensitive to Copper oxidation.